Ranging is a process of determining the distance from one position to another position. The various types of ranging systems (namely, RAdio Detection And Ranging (RADAR), LIght Detection And Ranging (LiDAR), and LAser Detection And Ranging (LADAR)) transmit and receive electromagnetic energy. The ranging system (also referred to as “rangefinder” or “ranging equipment”) includes a signal generator and transmitter that transmit an electromagnetic signal to a targeted object. The electromagnetic signal interacts with the targeted object, which reflects a portion of the electromagnetic signal. The ranging system includes a receiver that receives the reflected electromagnetic signal and transforms the captured energy into an electrical signal that can be processed by a signal processor. The ranging systems are connected to a computer or other electrical signal processing circuitry that extracts desired information. The computer also includes a high frequency clock that measures the time elapsed between the time the transmitter transmitted the electromagnetic signal and the time the receiver received the reflected electromagnetic signal. The computer uses the time elapsed to calculate the distance from the ranging system to the targeted object. For example, if the object is to be a target of gun firing, then based upon the return range output from the rangefinder, the computer can use laws of ballistics to determine the angle at which to set a gun barrel in order to impact the targeted object.
There are several methods and test equipment to test a rangefinder. One solution is an outdoor range technique that uses an outdoor range and a real target object (e.g., target board). The outdoor range technique includes opening a window to an outdoor range; firing a laser signal to a target (e.g., target board) that is disposed across the range at a distance away, such as 500 to 1000 meters away; receiving reflected laser signals from the reflection off the surface of the target, measuring the elapsed time between transmission and reception of the laser signals; and calculating the distance to the target using the elapsed time. The techniques for testing the rangefinder provide the rangefinder with one-dimensional information, namely the elapsed time in the time dimension.
Similarly for testing LADAR or LiDAR, the outdoor range technique can be utilized, where the target board is replaced by a real world target with depth, sometimes moving, or several targets in different locations and ranges. Similarly, large indoor facilities can accomplish LADAR/LiDAR testing via scaled down versions of the outdoor test facilities using giant collimators. However, small laboratory or portable indoor LADAR/LiDAR testing is currently limited to one dimensional targets at one range similar to laser rangefinder testing. Otherwise, compact indoor LADAR/LiDAR testing is limited to indoor testing of LADAR/LiDAR components via methods such as indoor testing of detector responsivity, detector noise, optical output power, uniformity, and boresight. There currently is a lack of LADAR/LiDAR system testing techniques that can be implemented using portable or small laboratory indoor LADAR/LiDAR test equipment, which is what this patent addresses.